Then Professor Conn applies his mechanics and chemistry to the respiratory process and, of course, makes out a very clear case till he comes to the removal of the waste, or ash. The steam-engine cannot remove its own ash; the "living machine" can. Much of this ash takes the form of urea, and "the seizing upon the urea by the kidney cells is a vital phenomenon." Is not the peristaltic movement of the bowels, by which the solid matter is removed, also a vital phenomenon? Is not the conception of a pipe or a tube that forces semi-fluid matter along its hollow interior, by the contraction of its walls, quite beyond the reach of mechanics? The force is as mechanical as the squeezing of the bulb of a syringe by the hand, but in the case of the intestines, what does the squeezing? The vital force? When the mechanical and chemical concepts are applied to the phenomena of the nervous system, they work very well till we come to mental phenomena. When we try to correlate physical energy with thought or consciousness, we are at the end of our tether. Here is a gulf we cannot span. The theory of the machine breaks down. Some other force than material force is demanded here, namely, psychical,--a force or principle quite beyond the sphere of the analytic method. Hence Professor Conn concludes that there are vital factors and that they are the primal factors in the organism. The mechanical and chemical forces are the secondary factors. It is the primal factors that elude scientific analysis. Why a muscle contracts, or why a gland secretes, or "why the oxidation of starch in the living machine gives rise to motion, growth, and reproduction, while if the oxidation occurs in the chemist's laboratory ... it simply gives rise to heat," are questions he cannot answer. In all his inquiries into the parts played by mechanical and chemical laws in the organism, he is compelled to "assume as their foundation the simple vital properties of living phenomena." VI